In this study, we investigated whether skeletal muscle mass estimated by brain CT could be used to predict neurological outcomes in neurocritically ill patients. Major findings of this study were as follows. First, a half of the surviving patients had a favorable neurological prognosis in this study. Second, during initial and follow-up CT, the TMT values of the poor neurological outcome group were significantly lower than those of the favorable neurological outcome group. However, during initial and follow-up CT, the C1-CSAs were not significantly different between the two groups except for initial C1-CSA/BSA. Second, in multivariable analysis, age, BMI, use of mannitol, and changes in C1-CSAand TMT were significantly associated with poor neurological outcomes in neurocritically ill patients. Especially, the risk of poor neurological outcome was proportional to changes of C1-CSA and TMT.
Nutritional support is an important issue in intensive care of critically ill patients [1–3]. Malnutrition is also associated with poor clinical prognosis of neurocritically ill patients [6, 7, 24]. Inadequate nutritional support increases susceptibility to infection, mortality, and neurological outcomes in these patients [6, 7, 24, 25]. Malnutrition has been estimated depending on various parameters that may include BMI, serum albumin and skeletal muscle mass [2]. However, BMI and serum albumin are poor parameters representing nutritional status in critically ill patients [1, 2]. Skeletal muscle mass is a more accurate parameter in assessing nutritional status and may reflect the clinical prognosis better than other nutritional measures in critically ill patients [2].
The CSA of skeletal muscle mass has been estimated via abdominal CT at third lumbar vertebral level, which correlates with the total body skeletal muscle mass and can be easily measured on an abdominal CT acquired during intensive care [12, 14, 26, 27]. Recent studies showed that CSAs of skeletal muscle mass at the level of cervical vertebrae on a head and neck CT scan significantly correlate with those at third lumbar vertebral level on abdominal CT scan [14, 28]. In addition, TMT also correlates with CSAs of skeletal muscle mass at third lumbar vertebral level or total psoas muscle area on abdominal CT scan [15, 16]. Therefore, CSAs of skeletal muscle mass at the cervical vertebra levels and TMT on brain CT can be used as alternatives to estimate sarcopenia and nutritional status in neurocritically ill patients.
Sarcopenia generally occurs in critically ill patients and may progress after ICU admission [29]. Skeletal muscle mass begins to decrease remarkably within 3 days and gradually deteriorates [3, 29]. In addition, the muscle mass of the limbs can be reduced by one-fifth within 7 days after ICU admission due to malnutrition and prolonged immobility as a consequence of critical illness [29, 30]. Skeletal muscle mass plays an important role in physiological functions such as immune modulation, protein synthesis and glucose metabolism [2, 11]. Therefore, sarcopenia secondary to critical illness is associated with adverse clinical prognosis [12, 13]. Similarly, malnutrition during the first week could be associated with poor neurological outcomes in patients with stroke [6]. Therefore, sarcopenia in the first week may be associated with poor neurological outcomes in neurocritically ill patients as well. In this study, changed muscle mass at first week was also associated with prognosis in neurocritically ill patients.
This study has several limitations. First, this was a retrospective review. Thus, GOS was determined based on medical records. Any bias involving the scores was mitigated partially based on the consensus of two independent specialists. Second, the nonrandomized nature of registry data might have resulted in selection bias. Brain CT scans were not protocol-based in their performance. Third, TMT of the surgical direction was not available because of possible damage and mobilization of the temporalis muscle occurring during either dissection, transsection, or incision after temporal craniotomy [31]. Lastly, our study has limited statistical power due to its small sample size. Although it still provides a valuable insight, prospective large-scale studies are needed to confirm the role of brain CT-based muscle mass measurement in predicting the clinical prognosis of neurocritically ill patients to arrive at evidence-based conclusions.